This is a good point, though for the sake of discussion imagine that JS didn't exist, and had no ecosystem at the time Node came on the scene. Do you assume it would have been conceived for that purpose?
Arguably Node took off because it allowed an already-existing huge ecosystem of libraries, tools, and developers to be leveraged for the back end, with all of those resources in turn coming from the browser.
I'd argue that Node took off because it was a greenfield environment where nearly everything was encouraged to use the event loop for asynchronous programming, so everything worked nicely together
> Node took off because it allowed an already-existing huge ecosystem of libraries, tools
It didn't. JS didn't have a huge set of existing tools and libraries when Node showed up. And the ones that did exist certainly didn't work in Node, considering they were written for the browser without a care in the world for other environments.
Arguably Node took off because it allowed an already-existing huge ecosystem of libraries, tools, and developers to be leveraged for the back end, with all of those resources in turn coming from the browser.